Switchboard for telephone-lines.



TED STATE-s PATENT OFFICE.

FRANK R. MCBERTY5LOF EVANSTON, ILLINOIS, ASSIGNOR TO THE WESTERNELECTRIC COMPANY,QOF CHICAGO, ILLINOIS.

SWITCHBOAR'D FOR TELEPHONE-LINES.

SPECIFICATION forming part of Letters Patent No. 654,750, dated July 31,1900. Application filed December 26, 1899. Serial No. 741,577. (Nomodel.)

To aZZ whom it may concern:

Be it known that I, FRANK R. MCBERTY, a citizen of the United States,residing at Evanston, in the county of Cook and State of Illinois, haveinvented a certain new and useful Improvement in Switchboards forTelephone- Lines, (Case No. 81,) of which the following is a full,clear, concise, and exact description,

This inventionconcerns apparatus for supervising and switching telephonelines equipped for the automatic control of signals and for the supplyof current for exciting the substation-transmitters from a centralsource in the switchboard.

The invention comprises several features, which have for their purpose,respectively, to provide for the automatic operation of lineannunciatorsand for the automatic elfacement of the displayed line-signals in makingconnection with the lines, to provide for severing the normal extensionsof the line-circuit through the line-signals in the case of such linesonly as must be free from grounded connections during their use, tofurnish means for exciting supervisory signals temporarily associatedwith united lines, and to avoid unnecessary current-disturbances inlines in the process of switching them together.

The invention has in View the adaptation of existing switchboards,particularly the socalled bridging-boards, to signaling and; supplyingcurrent for the transmitting-tele phone from a central source in theswitchboard.

' In the bridging apparatus referred to each,

telephone-line is provided with a spring-jack in each section of themultiple board of the type represented in Patent- No. 400,969, datedApril 9, 1889, to H. B. Thayer, or some essentially-similarform withplugs adapted to the spring-jacks and with a line-signal in somesectionofthe switchboard like that described in Patent No. 634,095,dated October 3, 1899, to C. E. Soribn'er,(Case No. 252.) h Thespringjacks not being specially adapted as agents for applying acontinuously-fiowing current in the switchboard are subject toaccidental contacts, which create troublesome noises in the telephonesof lines in the process of uniting them. The line-annunciators arepermanently connected in bridges of the lines, and

no means is provided for breaking these annunciator-bridges in specialcases where they prevent the normal operation of the line, such aslong-distance connections or party-lines adapted for selectivesignaling. .The present invention aims to obviate these variousobstacles to the employment of a common source of current in thebridging-board and to secure the advantages of automatic signals incommon battery-transmission therein. To this end its several featuresconsist in the following apparatus and circuits: In connection with thelocal circuit of each selectivesignal line which traverses therestoring-magnet of the line'annunciator thereof is arranged anelectromagnetic switch or cut-01f relay, of which the switch-contactscontrol the bridge including the actuating-magnet of thelineannunciator. With that contact-piece of the plug which is designedto close this local circuit and in so doing to come into direct connection with a battery applied to a local contact-piece of the jack Iassociate a third flexible conductor, forming the terminal of a circuitincluding the supervisory signal, together with a resistance-coil, and Iprovide in the plug-circuit the usual supervisory relay controlling ashunt about the signal, the plug-circuit being equipped with a bridgeincluding the common source of current, and for the purpose ofpreventing the formation of abnormal currents in the process of makingconnection with the line called for the tip or testing contact of thecalling plug is normally 8 5 disconnected from the remainder of theplugcircuit, its connection therewith being controlled by the operatorstelephone-key, and is connected with special appliancesto permitmakingthe test. p I

The invention is diagrammatically illustrated in the attached drawing.At the substation the transmitting and receiving telephones are placedin a normally-openbridge of the line which is closed bythe, telephone- 5switch when thetelephone is taken for use. The polarized call-bell isplaced in a permanently-closed bridge of the line,in which a condenseris interposed to prevent the passage of continuous current from thecentral bat- I00 tery through this bridge. The line conductors 1 and 2are led from the instruments at nunciator is includedjin a conductor 3,which forms a part of thelocal-batterycircuit 3 4, g which is open atnormally-separated multiple terminals d and d of the spring-jacks a anda.

As will be observed from the Patent No. 400,969 before mentioneddescriptive of the spring-jacks the springs d, which form the terminalsof thebaittery of all the spring-IT jacks in a strip in the switchboard,are formed integral with a ribbon of metal in the strip of spring-jacks."In lines like that extending to station E, which may be a party-line ora noisy line, which it isdesiralole to free from permanent groundbranches in the exchange during the use of the line, a cut-off relay fis provided which is preferably connected in a multiple. branch of theconductor 3 in parallel with the restoring-magnet of theline-annunciator, its

switch-contacts being interposed in the extensions of line conductors 1and 2 of the corresponding line. It may, however, if desired, be placedin series with the restoringmagnet in the same conductor.

' Plugs g and g are furnished in the switchboard united by aplug-circuit 5 6 and 7 8. Conductors 5 and 7 are united into a closedcircuit through a wire 9, which closed circuit includes two windings ofa repeating-coil h. Similarly, conductors 6 and 8 form a closed circuithaving a portion of the bridged conductor in common with the circuitbefore traced, the latter circuit including two other windings of thesame repeating-coil. The bridge of the plug-circuit thus formed leadsthrough thecommon source of current a, or, in other words, the point ofjunction of wires 5 and 6 is connected with earth, while the point ofjunction of wires 7 and Sis connected with the free pole of battery 0.Conductors 7 and 8 include each the magnet-winding of a supervisoryrelay/the latter being designated '11 and 1;. Each of these relayscontrols the display, of a secondary supervisorysignal k or Zr. Thesleeve of each plug, which in the bridging-board is not utilized astheter minal of a circuit but merely serves to cross together thecontact-pieces d and d of a springjack into which it is inserted, nowbecomes the terminal of a conductor which includes the secondarysupervisory signal, together with a resistance-coil. Thus conductor 10,terminating in the sleeve of plug g, includes the signal-lamp 7c and theresistance-coil m. The sleeve'of the other plug is the terminal ofconductor 11, which includes the supervisory signal and theresistance-coil m, The means whereby either supervisory relay con-,trols its secondary signal is a shunt of the signal traversing theswitch-contacts of the relay.

Each pair of plugsis furnished with the usual calling-key for applying asource of callingcurrent to the plug g, which for the sake of clearnessis not shown in the drawing, and with a listeningkey 'n for bringing theoperators telephone 0 into a bridge of the plugcircuit. This operatorskey is designed to break the continuityof. the conductor 8, while thetelephone is'applied' to the circuit and to connect the portion of theconductor leading to the tip of the plug directly with one side of .theoperators telephone for the purpose of testing, at the same timeinterpo'sing a condenser in the break thus produced in the conductorTS.Thusinthe normalposition of the telephone-key the conductor 8 iscomplete. While the telephone is connected with the plug-circuit, thecircuit of the common battery to the tip of the plug is broken, whilethe inductive continuity of the circuit ismaintained to permit thetransmission of telephone-currents through the operators telephone. J v,

' Taking the telephone for use at the .substation by closing theline-circuit through the telephones there produces a current through theindividual line-signal b, which displays the indicator of theannunciator. The oper ator answering the call inserts plug gjnto theanswering-jack a of the calling-line. Thereby the conductors 3 and 4 ofthe local circuit are united through the sleeveof the inserted plug, therestoring-magnetof theline-annum ciator is excited, and thedisplayedindicator is replaced. At the same time a branch circuit is formed fromthe conductor 4, through the sleeve of the plug and conductor 10teri'ninating therein, which the supervisory signal In is incited. Theinsertion Of the plug into the spring-jack a produces, however, acircuit for the batteryc through the conductors 5 and 7 of theplug-circuit to the telephone-line, and a current flowing in thiscircuit excites the supervisory relayi and closes the shunt about thesignal It, whichthus remains concealed. vHaving learned the sub-'scribers order for the required connection,the operator tests the linecalled for .by applying the tip of plugg to thetest-ringofaspringjackjthereof, the operators listening-key being still inposition to connect her telephone with the plug-circuit. ,If theconductors 3,

leading to the testrings of the line tested, be.

connected with the conductor i, leading to the free pole of the localbattery, current will flow at each application of, the test-plug"through the conductor 8 ofthe plu'g circuit and a portion of theoperators telephone to earth, which will indicate the busy condition ofthe line. in the telephone, the operator inserts the plug 9 fullyintothe spring jack. As the plug is thrust into the spring jack the tipgofthe plug comesin contact successively with the thimble of thespring-jack,with the battery-spring,

with the longer line-spring, and, finally, with ;the shorterline-spring; but inasmuch as the plug is disconnected .from'the batteryin the If no busy-test click is heard plug-circuit no currents areproduced by the accidental contacts in the jack of sufficient strengthto be troublesome in the telephone of the calling subscriber. When theplug is in place, the operator disconnects her telephone from thecircuit, whereby connection of the common battery 0 with the called lineis completed. The called line is in this case a partyline and isfurnished with means for breaking the normal bridge of the lineincluding the line-annunciator. When the plug is inserted in the jack tocomplete the connection, the local circuit 3 4 is closed and the cnt-oitrelay f is excited, leaving the line free from all unnecessaryconnections in the switchboard. Current in the same local circuit thusformed excites the supervisory signal which latter remains displayeduntil the subscriber called removes his telephone from its switch foruse, when the signal becomes shunted by the supervisory relay. Theresistance-coil in circuit with the signal in each of the conductors 10and 11 maintains a sufficient difference of potential to permit theshunting of the signals withoutundue waste of energy. In practice thesignals may be of, say, ten ohms and the coils of thirty ohmsresistance.

The invention is defined in the following claims:

1. The combination with a telephone-line, a spring-jack forming aterminal of the line, and a plug and plug-circuit for making connectionwith the spring-jack, of a local circuit terminating innormally-separated opposed contacts of the spring-jack adapted to becrossed together through the sleeve of the plug, and a magnet in thelocal circuit, a branch of the local circuit terminating in saidcontact-sleeve of the plug, a secondary supervisory signal in the last-mentioned branch, and a supervisory relay in the plugcircuitcontrolling said signal, as described.

2. The combination with a telephone-line, a self-restoringline-annunciator thereof, a spring-jack forming a terminal of the linein the switchboard, and a plug and plug-circuit for making connectionwith the spring-jack, and a local-battery circuit terminating innormally-separated contact-pieces of the spring-jack adapted to becrossed together through a local contact-piece of the plug,said localcircuit including the restoring-magnet of the annunciator,of asupervisory relay and a source of current in the plugcircuit, a branchof the said local circuit in multiple with the restoring-magnet, asecondary supervisory signal and a resistance-coil in said branch, and ashunt of the secondary signal controlled by the supervisory relay; whereby the line-annunciator is reset and the sec ondary signal is excitedfor control by the relay when connection is made with the line, asdescribed.

3. The combination with a telephone-line and a self-restoringline-annunciator in a normal bridge of the line-circuit,a spring-jackfor the line, and a local circuit including the restoringmagnet of theline annunciator and normally open at separated contacts in thespring-jack adapted to be closed together by an inserted plug, of anelectromagnetic switch controlling the bridge of the line-circuit, theactuating-magnet of the said switch being in the same local circuit withthe restoring-magnet of the line-annunciator, as described.

4:. The combination with telephone-lines and a plug and plug-circuitforminga tempo ary extension of one of the lines, a source of currentconnected with the plug-circuit, and an operators listening-key,ofswitch-contacts on the listening-key adapted to connect the telephonewith the plug-circuit and to sever the conductive connection between thetip of the plug and the said battery; whereby the plug may be insertedinto the spring-jack of a line without producing disturbances in thetelephone of the line connected with the plug as described.

In witness whereof I hereunto subscribe my name this 5th day of October,A. D. 1899.

FRANK R. MCBERTY.

WVitnesses:

ELLA EDLER, FLORENCE E. SUMMERS.

